Apparatus for binding sheets

ABSTRACT

Apparatus for binding a stack of sheets in which the stack is aligned on an edge to be bound and clamped in the aligned position with the edge exposed for binding. A binding tape has thermoactive adhesive arranged on one exposed side in a pattern of discrete deposits. The tape and edge are then simultaneously heated until the adhesive flows in a fluid state from the discrete deposits to cover the tape. The adhesive on the tape is then pressed against the exposed edge of the stack and wiped around stack sides adjacent the edge to bind the stack of sheets.

United States Patent [191 Dornemann et al.

[ 1 Feb.6, 1973 APPARATUS FOR BINDING SHEETS [73] Assignee: USM Corporation, Boston, Mass.

[22] Filed: Dec. 17, 1970 [21] Appl. No.: 99,002

[56] References Cited UNITED STATES PATENTS I Hofe et al. 156/499 X l/l968 Hawkes ct al ..l56/477 B 9/1970 Rost et al ..l56/499 X Primary Examiner-Edward G. Whitby 'Att0rneyRicha rd A. Wise and Richard B. Megley [57] ABSTRACT Apparatus for binding a stack of sheets in which the stack is aligned on an edge to be bound and clamped in the aligned position with the edge exposed for bind ing. A binding tape has thermoactive adhesive arranged on one exposed side in a pattern of discrete deposits. The tape and edge are then simultaneously heated until the adhesive flows in a fluid state from the discrete deposits to cover the tape. The adhesive on the tape is then pressed against the exposed edge of the stack and wiped around stack sides adjacent the edge to bind the stack of sheets.

7 Claims, 15 Drawing Figures PATENTEDFEB slsrs 3.715260 SHEET 10F 7 in van fans Peler LDorrzeman-rz All H077, R FadcZz'f/e Alem 5 Newton- Samuel E. Fafon Jr By fizeir Azzorney PATENTEDFEB 61m SHEET 3 OF 7 PATENTED FEB 6 I575 SHEET '4 OF 7 PATENTED 6 I573 3.715.260

SHEET 6 BF 7 PATENTEDFEB 6mm 3,715,260 SHEET 70F 7 APPARATUS FOR BINDING SHEETS BACKGROUND OF THE INVENTION This invention relates to apparatus for binding loose sheets in book form with thermoactive adhesive on a binding tape.

Conventional binding entails assembly of sheets of paper into groups of folded sheets called signatures and securing the signatures by stitching or stapling. Groups of signatures are then assembled in book form and a binding applied. Solvent activated adhesives are traditionally used to apply bindings.

More recently, thermoactive adhesives have been used to provide quicker and stronger adhesion of bindings. Thermoactive adhesives strong enough to eliminate the need for signatures may be used. The thermoactive adhesive is heated in bulk and applied to a stack of sheets in liquid form. Bulk heating of thermoactive adhesive is a time consuming process, especially where only occasionalbinding is performed. Ad-' ditionally, applying liquid adhesive is frequently an untidy operation.

Still more recently, tapes coated with thermoactive adhesive have been used for bindings. These tapes tend to curl when heated. Curling of the tape results from the differing coefficients of thermalexpansion of the tape and adhesive. Such curling moves the tape from a position aligned with an edge of the stack of sheets to be bound and causes the adhesive on the tape to contact the structure supporting the tape. Movement of the tape results in an esthetically displeasing, crooked binding and may leave some sheets unbound. The binding thus produced is unsatisfactory. Contact of the adhesive with the supporting structure deposits adhesive on the structure and prevents separation of the tape from the structure. The machine may thus become inoperative or untidy.

Frequently the sheets to be bound were not heated prior to the application of thermoactive adhesive thus reducing the penetration of the adhesive between the j sheets. The resulting bindings were not strong.

In addition, indirect heating of the adhesive through the tape as taught by the prior art precludes the use of easily melted, plastic binding tape materials which provide a desirably smooth and esthetically pleasing appearance. Indirect heating also contributes to undesirable curling of the tape.

SUMMARY OF THE INVENTION Accordingly it is an object of the invention to provide a method and apparatus for binding sheets which provides a quick, tidy and strong thermoactive adhesive binding.

It is a further object to provide a thermoactive coated tape for use in the apparatus which will not curl when activated for binding.

In carrying out the method of the invention, the sheets are stacked with edges aligned in a common plane to form a substantially smooth edge face on the stack for binding. The stack has broad sides adjacent the edge face formed by the end sheets of the stack. The stack is clamped to maintain the alignment of the sheets with its edge face exposed for binding. A strip of binding tape of a width determined appropriate for binding the stack and having thermoactive adhesive on one side is cut from a larger piece of tape and placed in aligned, spaced relation to the edge face of the stack. Heat is then applied simultaneously to the adhesive on the tape and to the edge face of the stack to be bound. Sufficient heat is applied to the adhesive to activate it. The edge face of the stack is heated preparatory to binding to insure penetration of the adhesive into the stack for a strong binding. The tape may also be heated simultaneously with the adhesive and edge face..The adhesive is then pressed against the edgeface of the stack by the tape to form the binding. Desirably the tape is wider than the edge face of the stack and the excess width of the tape may be wiped around the edge face and against one of the broad sides of the stack. The adhesive secures the tape to the edge face to bind the stack of sheets.

The apparatus for carrying out the above method has an aligning table. A stack of sheets is aligned by placing an edge face of the stack firmly on the table. A clamp near the table grips broad sides of the stack to support and retain the alignment of the stack. The clamp leaves the edge face and an adjacent portion of the broad sides exposed for binding. A pressure pad spaced from the side of the table opposite the clamp supports a width of binding tape determined to be appropriate for binding the stack and having thermoactive adhesive on one exposed side. The determined width is then cut from a larger piece of tape to form a strip. A heat source then heats the adhesive and the edge of the stack on the table. The heat activates the adhesive and prepares the edge face for binding. The tape may also be simultaneously heated. The table and heat source are then removed, and the clamp gripping the stack and the pressure pad moved relatively toward each other to press the adhesive on the tape against the exposed edge face of the stack. Desirably a wiper bar in spaced alignment with a face of the clamp may press the tape and adhesive against the broad side of the stack immediately after the pad presses the tape and adhesive against the edge face of the stack..The adhesive secures the tape to the stack to bind the stack of sheets.

A binding material for use in the above apparatus has thermoactive adhesive arranged in discrete deposits on one side of a tape. The thermoactive adhesive is of a type which is activated to a fluid, sticky state by heat. The deposits are discrete in that adjacent deposits have substantial discontinuities between them and are not in major contact with each other. Because the deposits are discrete, their thermal expansion is not cumulative. The difference in linear expansion of a discrete deposit and the area of any tape material covered by the deposit is thus minimized. Additionally, the tape surface between deposits is heatable simultaneously with the adhesive deposits. The tape and adhesive thus trend to remain at substantially equal temperatures throughout the heating time. The resulting simultaneous thermal expansion of the tape and adhesive minimizes transient differences in thermal expansion between the tape and adhesive. Minimizing the difference in linear thermal expansion between the adhesive and the tape minimizes curling and consequent movement of the tape. Desirably the deposits are so made that the tape will not curl when the adhesive is activated by heat.

BRIEF DESCRIPTION OF THE DRAWINGS ,The above and other features of the invention will be more fully understood in conjunction with the drawings, wherein:

FIG. 1 is a perspective view of the apparatus;

FIG. 2 is a side view of the apparatus with the case removed to show internal parts;

FIG. 3 is a side view of the apparatus similar to FIG. 2 but with certain parts in different positions;

FIG. 4 is an exploded perspective view of certain parts shown in FIG. 3;

FIG. 5 is an exploded perspective view of certain parts shown in FIG. 4;

FIG. 6 is a perspective view of the parts shown in FIG. 5 in a different position;

FIG. 7 is a sectioned perspective view of certain parts shown in FIG. 4 with a section of a stack of sheets shown in position to be bound;

FIG. 8 is a side view of the apparatus showing certain parts not seen in FIG. 2;

FIG. 9 is a front view of a knife structure of the apparatus;

FIG. 10 is a perspective view of a bound stack of sheets;

FIG. 11 is a top view of the preferred embodiment of material for use in the apparatus of FIG. 1;

FIG. 12 is a side view of the material in FIG. 11;

FIG. 13 is a side view of an alternative embodiment of material for use in the apparatus of FIG. 1;

FIG. 14 is a side view of another alternative embodiment of material for use in the apparatus of FIG. 1; and

FIG. 15 is a top view of still another alternative embodiment of material for use in the apparatus of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a stack of sheets S is firmly placed on a table 10 to align a narrow end of each sheet with other sheet ends to form an edge to be bound on the stack. A clamp 12 engages a broad side of the stack to support the stack between the clamp and a frame 14 of the machine. A width of tape appropriate for binding is fed to the top of a flexible pressure pad 16 below the stack. Heating elements under the table are then energized to activate thermoactive adhesive on the side of the tape facing the stack and to heat the edge of the stack on the table to prepare the edge for receiving the tape. The table is then moved from under the stack and the pressure pad raised to press the tape on the pad against the edge of the stack. The adhesive on the tape penetrates into the heated edge of the stack and cools to adhesively secure the tape to the stack to bind the stack of sheets.

The table 10 for aligning the stack comprises a rectangular frame having a plurality of spaced transverse support members indicated generally at 18 passing beneath and supporting each sheet of the stack carried edgewise thereon. The table is thus substantially transparent to heat to permit the direct heating of the edge of the stack from a heat source under the table. Transparent to heat shall mean that heat, in any desired form, passes through the table by radiation, conduction or carrier medium as appropriate to the form of heat.

The table, one end of which is shown in FIG. 2, is rollingly supported at each end by a pair of wheels 20 mounted in a track 22 secured to a frame of the machine. The table rolls from a position beneath and supporting the stack to a position remote from the stack (see FIG. 3).

The clamp 12 has a plate having a broad face 24 for engaging the broad side of the stack. A shaft 26 rotatably connected to the plate has segmented threads in threaded engagement with segmented threads in a nut 28 non-rotatably secured to a bracket 23 'connected to the machine frame. The segmented threads permit the clamp to be first slid against the stack S and then tightened against the stack by rotating the shaft into threaded engagement with the nut. The stack is thus securely held between the face of the clampand the frame 14 of the machine. The table 10 may thus be withdrawn from under the stack without disturbing the alignment of the stack.

The clamp 12 and frame 14 do not engage the lower portions 13 of broad sides of the stack adjacent the edge to be bound so that binding tape may be wiped against the portions of the sides. To prevent the edge of the stack from fanning out where it is not engaged by the clamp and frame, movable gates 25 and 27'are slidingly supported in the clamp 12 and frame 14, respectively. The gates project below the clamp and frame and have bar faces 29 and 31 in spaced alignment with the faces of their respective supporting structures for engaging the portions 13 of the stack to prevent fanning of the stack. During the binding operation each gate is slid vertically upward to expose. the portions 13 of the stack for receiving binding tape. The stack will not then fan out because it is then bedded against the pressure pad 16 as described below. To raise the gate 25 is the clamp,the gate is provided with a lifting arm 33 projecting laterally from the upper end of the gate above the clamp. To raise the gate 27 in the frame, a lifting arm 35 projects downwardly and laterally from the face 31. The lifting arms 33 and 35 are engaged by lifting members as described below to lift the gates vertically away from the stack portions 13 to be bound.

Tape 30 is fed to the upper surface of the pressure pad from a roll 32 rotatably mounted on the machine frame. The tape is fed between a pair of cooperating feed rollers 34 and 36 which are spring-biased toward each other to firmly engage the tape. The roller 36 is connected to a ratchet mechanism (not shown) for rotation only in a clockwise direction to feed the tape to the right as seen in FIG. 2. The ratchet mechanism is operatively connected by gear and chain drive generally indicated at 38 to a knob 40 (in FIG. 1). Clockwise rotation of the knob thus rotates the roller 36 to feed tape between the rollers. counterclockwise rotation of the knob does not rotate the rollers because of the ratchet mechanism. The tape is thus fed into the machine but may not be inadvertently unthreaded from the feed rollers 34 and 36.

The chain drive 38 has a section generally indicated at 42 which passes adjacent an abutment 44 on a portion of the machine frame and an abutment 46 on an arm 48 secured to and depending from the clamp 12. A link of the chain section 42 between abutments 44 and 46 is provided with an enlarged stop member 50 for contact with the abutments. Movement of the chain is thus restricted to the distance between the abutments. In operation, the stop member is first moved to the abutment 44 by counterclockwise rotation of knob 40. The ratchet mechanism prevents movement of the feed rollers and the tape. Clockwise rotation of the knob 40 then rotates the roller 36 to feed the tape until the stop 50 engages the clamp arm abutment 46. Since the clamp engages the stack, the position of the clamp is determined by the thickness of the stack S, and the width of tape 30 fed by the feeding means is also determined by the thickness of the stack. A width of tape appropriate for binding the stack is thus determined.

The tape fed by the feeding means is directed to a cutter generally indicated at 52 (FIG. 2) by a slotted member 54. A guide 56 connected between opposite sides of the machine frame aligns the tape with the adjacent pressure pad 16 for feeding the tape to the pressure pad.

The cutter 52, as seen in FIG. 9, has a knife support 62 at least as long as the rolled tape slidably mounted for vertical movement between opposite sides of the machine frame. The knife support is operatively connected by a scissors jack 64 and chain drive 66 to a knob 68 (shown in FIG. 8). Rotation of the knob is thus effective to raise or lower the knife support. A knife is carried by the knife support with blades disposed in the plane of sliding motion of the support. The blades of the knife have points 70 and sharpened edges 72 inclined from the points towards the support and are inclined from the direction of sliding movement of the knife support so that the point of one blade overlaps the edge of an adjacent blade. Upward movement of the knife support thus moves the blades against the tape which is held against movement by a top member 71 secured to the frame over the guide. An edge 73 of the top member cooperates with the points of the blades so that they first pierce the tape and the edges of the blades then slice the tape to cut a width of tape from the roll. Any tape not fully cut by the piercing point will be sliced by the overlapping blade. To insure a smooth cut, a bar 74 is connected to the knife support by springs 76 to resiliently grip the tape between the bar and the top member 71 when the knife support is raised to cut the tape.

In FIG. 8 heating elements 78 are seen to be mounted on the lower side of the table for directly heating the edge of the stack on the table and the adhesive side of the tape 30 on the pressure pad. The heating elements are a plurality of tubular quartz lamps extending beneath the entire length of the table. The lamps radiate heat directly to the stack and the adhesive on the tape. The spaces between the support members 18 make the table transparent to the radiated heat to permit the direct heating of the stack; heating the stack decreases the surface tension effects of the stack for greater penetration of adhesive when the binding is applied. Heating of the adhesive side of the tape activates the thermoactive adhesive most fully at the edge of contacting surface and eliminates heat losses in the tape. The tape may thus be made from a material such as vinyl which is sensitive to temperatures close to those required for activating the thermoactive adhesive.

Returning to FIG. 1, a switch 80 is effective to energize the heating elements. A timing circuit (not shown) is preset to maintain the energization of the heating elements for a period of time predetermined to be sufficient for heating the adhesive and the edge of the stack. After the time period, the timing circuit turns off the heating elements and turns on an indicating light 82 to notify the operator that the tape and adhesive are ready for binding application to the edge of the stack.

A binding mechanism connected to a push bar 84 is effective upon operator movement of the bar toward the stack to apply the tape to the edge of the stack.

Rods 85 (one shown) connect both ends of the push bar 84 to the table 10. Operator movement of the bar toward the stack thus moves the table from its position beneath the stack to its position remote from the stack to expose the edge of the stack for binding.

-As seen in FIG. 2, the push bar is also connected to sliding cams 86 (one shown) having inclined cam surfaces 88 which engage a pivot shaft 90 centrally connecting a pair of lazy-tong elements secured at one end to either side of a pressure pad support 92 and at the other end to the machine frame. Contact of the cam surfaces 88 with the shaft 90 moves the shaft toward the stack and, through lazy-tong apparatus, the pressure pad on the pressure pad support moves into contact with the edge of the stack.

FIGS. 3 and 7 best show one of a pair of cams 94 connected to opposite ends of the push bar. Since operation of each cam 94 is the same, only one will be described. The cam 94 engages a roll 96 rotatably secured to one end of a lever 98 pivotally secured intermediate its ends to the pressure pad support 92. An inclined cam surface 100 of the cam 94 is effective to push one end of the lever 98 downwardly as the cam 94 is advanced toward the stack. The structure and direction of movement is now best indicated in FIG. 4. The other end of the lever 98 is pivotally connected to a parallel jack which is pivotally connected to the pressure pad support 92 by an arm 112 for vertical movement of the jack. Downward movement of the roll bearing end of the lever 98 is thus effective to produce vertically upward movement of the parallel jack 110. Because of the pivotal connection of the parallel jack to the pressure pad support, a lifting edge 114 on the upper side of the parallel jack moves vertically upward. One end of the lifting edge 114 contacts a pin 116 projecting from a movable wiper 118 adjacent and aligned with the pressure pad support and below the pressure pad. Upward movement of the parallel jack thus raises the wiper and the pressure pad. The wiper 118 is also in spaced alignment with the frame 14 of the machine against which the stack is clamped and thus in spaced alignment with a broad side of the stack. Movement of the wiper thus folds the pressure pad against a broad side of the stack. In order to insure that the end of the tape is firmly pressed against the broad side of the stack, the wiper 118 has a projection 120 (best seen in FIGS. 5 and 6) having a pin 122 parallel withthe pin 116 and spaced vertically downward from the pin 116. The pin 122 is received in a stepped slot 124 in a portion of the pressure pad support 92. Another pin 126 projects from a portion of the pressure pad support 92 and is received by a slot 128 in the projection 120 of the wiper 118. As the wiper 1 18 is raised by the parallel jack, the pins 122 and 126 slide in their respective slots to tilt the wiper toward the broad face of the stack. The end of the tape is thus firmly pressed against the broad face of the stack.

Referring again to FIG. 4 the parallel jack lifting edge 114 also engages a block 130 restingly supported on a portion of the pressure pad support 92. The block is connected to a vertical shaft 132 slidingly supported near its upper end by a sleeve 134 connected to the clamp 12. A laterally projecting arm 136 is secured to the upper end of the shaft for movement with the shaft and underlies the lifting arm 33 of the clamp gate 25. The lifting edge 114 also directly engages the lifting arm 35 of the frame gate 27. Upward movement of the parallel jack 110 is thus effective to raise the gates to expose the portions of the broad sides of the stack engaged by the gates for binding.

The block 130 is also pivotally connected to a wiper bar 140 having an edge 142 parallel with the broad side of the stack engaged by the clamp. The parallel relation of the edge 142 is provided by the sleeve connection of the shaft 132 with the clamp 12. The wiper bar 140 is weighted along the opposite edge by a weight 144. The wiper and weight are restingly supported below the pressure pad on a portion of the pressure pad support 92. As the block 130 is raised by the parallel jack 110, the edge 142 of the wiper 140 pivotally rises to press the pressure pad and the tape on the pad against the broad side of the stack engaged by the clamp. To insure firm contact of the wiper 140 with the side of the stack, a cam 146 is secured to a sleeve 147 on the shaft 132 intermediate the block 130 and sleeve 134. The cam 146 engages a cam surface 148 on the wiper 140 to rotate the wiper 140 in a clockwise direction as seen in FIG. 4. The cam 146 and sleeve 147 are held against movement when engaging the wiper 140 by a projection 149 on the cam 146 which engages the clamp 12.

Referring again to FIGS. 1 and 2, the pressure pad 16 on the support 92 is a soft, spongy sheet loosely placed over the wipers 118 and 140 and supported by the pressure pad support 92. A peg 150 projects centrally from the end of the pressure pad seen in FIG. 1. The peg 150 is resiliently connected to the pressure pad support by a spring 152 to return the pad to its initial position after a binding operation. To further insure the alignment of the pad, pegs 154, shown in FIG. 1, project from the pressure pad support through slots 156 in the pressure pad. Additional slots 158 pass transversely through the pad to provide space for thermal expansion of the pad to prevent curling of the pad when the tape on the pad is heated. The pressure pad is made from a spongy material to provide a resilient bed for pressing the tape against the stack. The resilient pad may typically bed the edge one-sixteenth inch in its surface. Small variations in the alignment of adjacent sheets of the stack are accommodated by the resilience of the pad so that the adhesive is firmly pressed against the end of each sheet in the stack.

When the tape and adhesive are firmly pressed against the edge and adjacent sides of the stack, the adhesive cools in the absence of heating means to adhesively secure the tape to the stack. The stack is then bound. The operator then releases the clamp 12 by first rotating the shaft threads out of engagement and then sliding the clamp away from the stack. The bound stack as shown in FIG. 10 may then be removed from the apparatus.

In an alternative embodiment of the invention, the pressure pad may be eliminated by employing a resilient tape or a thick layer of flowable adhesive or a resilient adhesive any one of which would provide the resilient bed for accommodating small variations in the alignment of adjacent ends of sheets of the stack.

As shown in FIGS. 11 to 15 the material for binding is a tape 30 or flexible sheet having discrete deposits of thermoactive adhesive 200. The discrete deposits of adhesive permit both the tape and the adhesive to be directly heated from the adhesive side of the tape.

Adjacent discrete deposits of adhesive are spaced on the tape surface by substantial discontinuities 202 in the adhesive. Since linear thermal expansion is a cumulative function of linear dimension, the discontinuities minimize the linear expansion of the adhesive. Additionally, the discontinuities permit the direct heating of the tape as well as the adhesive so that transient temperature differences between the materials are minimized. The discrete deposits thus eliminate the bi material strip structure of known tapes and adhesives and therefore the curling of the tape.

The discrete deposits of adhesive are additionally arranged so that any straight line drawn on the adhesive side of the tape and parallel to one edge of the tape from an edge to an opposite edge will intersect a deposit of adhesive. As shown in FIG. 11, the deposits subtend a circular base area on the tape of a radius greater than the minimum linear separation or discontinuity between adjacent deposits and are arranged in rows with the center of each deposit in a row on a line bisecting the discontinuities of adjacent rows. Additionally the deposits are of such size that more than one row is contained on a minimum width of tape determined by the apparatus. Thus each sheet in the stack will be adhesively bound at the site of at least one adhesive deposit to insure contact of each sheet with the adhesive.

The adhesive is heated until the thermoactive adhesive is activated to reach a fluid state. The discrete deposits of adhesive then flow by gravity from the deposits over the tape surface. The tape is thus covered with a substantially uniform coating of fluid thermoactive adhesive for binding. The adhesive may be any suitable thermoactive adhesive. Preferably the adhesive is that described in US. Letters Pat. No. 3,316,573, issued May 2, 1967 in the name of A.M. Chaplick, et al.

The tape may be made from any flexible sheet material able to withstand the heat required to activate the adhesive. Vinyl, paper, and cloth are suitable for use with the adhesive described in the above patent. Tape material which is permeable to fluid adhesive such as paper or cloth is coated with an impermeable but may be alternatively embodied in accordance with the teachings of the invention. I

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. An apparatus for binding a plurality of sheets,

which comprises:

a clamp for gripping broad sides of a stack of the sheets leaving an edge face of the stack exposed for binding;

a pressure pad for supporting a width of tape having thermoactive adhesive on an exposed side of the tape;

means for simultaneously heating the edge face of the stack preparatory to binding and the adhesive on the tape to activate the adhesive for binding; and

means for relatively moving the clamp and pressure pad toward each other to press the adhesive on the tape against the edge face to bind the stack.

2. An apparatus as in claim 1 additionally comprising: a movable wiper bar cooperative with one of the broad sides of the stack for wiping tape around the edge face and against the broad side of the stack, and means operative after the clamp and pressure pad press the adhesive against the edge face for moving the wiper.

3. An apparatus as in claim 1 additionally comprismg:

means for determining a width of tape appropriate for binding the stack,

means for feeding the determined width of tape to the pressure pad, and

means for cutting the determined width of tape from a larger piece of tape to form a strip of tape for binding the stack.

4. An apparatus according to claim 3 wherein the means for cutting the tape comprise:

a support bar slidably mounted on a machine frame;

a plurality of knife blades fixed to the support bar for engagement with the tape, the knife blades having a point and a sharpened edge inclined from the point toward the support bar for first piercing and then slicing the tape;

means for slidably moving the support bar perpendicularly to the tape for cutting the tape by engagement of the tape with the knife blades; and

means for holding the tape against movement with the blades upon cutting engagement with the blades.

5. An apparatus according to claim 1 wherein the means for moving the pressure pad comprise:

a ressure ad su ort for su ortin the ad; a jiiair of la zy-ton g connecti fi g oppt )site Ends of the pressure pad support to the machine frame and having a shaft centrally connecting the pair of tongs; and

a cam slidably mounted on the machine frame and having a cam surface for lifting the shaft upon sliding engagement with the shaft to lift the pressure pad.

6. An apparatus as in claim 1 additionally comprising an aligning table near the clamp on which the edge of the stack is placed for aligning the sheets of the stack wherein the table is transparent to heat from the heating means for heating the edge of the stack, while it is on the table, simultaneously with the adhesive.

7. An apparatus as in claim 1 wherein the clamp has a gate member engaging the broad side of the stack adjacent the edge face to prevent the stack from fanning out adjacent the edge face and movable from the position adjacent the edge face to a position adjacent the clamp to expose the broad sides adjacent the edge face for binding. 

1. An apparatus for binding a plurality of sheets, which comprises: a clamp for gripping broad sides of a stack of the sheets leaving an edge face of the stack exposed for binding; a pressure pad for supporting a width of tape having thermoactive adhesive on an exposed side of the tape; means for simultaneously heating the edge face of the stack preparatory to binding and the adhesive on the tape to activate the adhesive for binding; and means for relatively moving the clamp and pressure pad toward each other to press the adhesive on the tape against the edge face to bind the stack.
 2. An apparatus as in claim 1 additionally comprising: a movable wiper bar cooperative with one of the broad sides of the stack for wiping tape around the edge face and against the broad side of the stack, and means operative after the clamp and pressure pad press the adhesive against the edge face for moving the wiper.
 3. An apparatus as in claim 1 additionally comprising: means for determining a width of tape appropriate for binding the stack, means for feeding the determined width of tape to the pressure pad, and means for cutting the determined width of tape from a larger piece of tape to form a strip of tape for binding the stack.
 4. An apparatus according to claim 3 wherein the means for cutting the tape comprise: a support bar slidably mounted on a machine frame; a plurality of knife blades fixed to the support bar for engagement with the tape, the knife blades having a point and a sharpened edge inclined from the point toward the support bar for first piercing and then slicing the tape; means for slidably moving the support bar perpendicularly to the tape for cutting the tape by engagement of the tape with the knife blades; and means for holding the tape against movement with the blades upon cutting engagement with the blades.
 5. An apparatus according to claim 1 wherein the means for moving the pressure pad comprise: a pressure pad support for supporting the pad; a pair of lazy-tongs connecting opposite ends of the pressure pad support to the machine frame and having a shaft centrally connecting the pair of tongs; and a cam slidably mounted on the machine frame and having a cam surface for lifting the shaft upon sliding engagement with the shaft to lift the pressure pad.
 6. An apparatus as in claim 1 additionally comprising an aligning table near the clamp on which the edge of the stack is placed for aligning the sheets of the stack wherein the table is transparent to heat from the heating means for heating the edge of the stack, while it is on the table, simultaneously with the adhesive. 